The present invention relates to a catheter. The invention is particularly concerned with a catheter suitable for obtaining suprapubic access and drainage. The following description is mainly directed to this type of catheter, but it will be understood that the invention is also applicable to other types.
A suprapubic catheter is conventionally inserted through the abdominal wall into the bladder by means of trocar projecting through the catheter tip. The trocar is withdrawn when the catheter tip is in place. A variety of means have been proposed to ensure that once in place the catheter tip is retained in the bladder. For example, a Foley bladder catheter includes an inflatable balloon at its distal end (i.e. within the bladder), an inflation channel in the walls of the catheter, external means of supplying inflation fluid through the channel and valve means to keep the fluid in place and the balloon inflated.
An alternative retention means uses a resiliently protruding formation which can be elastically deformed by an actuator to the protruding position for retention and to a non-protruding disposition for catheter insertion and removal. Examples are (i) "wings" formed from the catheter wall [Malecot catheters]or (ii) an increased diameter portion of the catheter tube at its tip [De Pezzer].
The tip formation can for example be held in a protruding disposition by tension in an actuating rod or line which extends to the proximal end of the catheter (see British Patent Specification Nos. 688,450, 955,490, 1,014,570, 1,046,478 and 1,463,269 and U.S. Pat. Nos. 1,828,986, 3,241,554, 3,261,357, 3,713,447 and 4,228,802). U.S. Pat. No. 3,490,457 to Petersen discloses a catheter in which wings are brought into a projecting disposition by pulling on a tip insert with a thread which extends the length of the catheter tube to its proximal end. When the wings are erect, the thread is removed.
For many purposes, the most convenient combination of catheter tubing and actuating means for effecting the expansion and contraction of a distal protruding portion is provided by employing two concentric tubes secured together at their distal ends, the inner tube providing a fluid flow passage and the outer tube incorporating near its distal end an expandable portion which can be brought into its protruding position by relative axial movement of the two tubes. An early example of such concentric tube catheters is described in U.S. Pat. No. 3,108,595 to Overment. A later example, U.S. Pat. No. 3,946,741 to Adair, relates to the provision of sealing means to prevent leakage through the outer tube.
Problems arise in using catheters with such expandable tip portions in ensuring or checking whether the tip is in the expanded or contracted position inside the body. Although in principle it is possible to check by inspecting the external portions of the catheter, this is only satisfactory if the person making the inspection is sufficiently familiar with the particular catheter to know what internal position is indicated by the relative external position. Thus in practice there arises the likelihood that the catheter tip will be left in the body with its intended protruding portion in the contracted state, and thus vulnerable to being inadvertently removed from the body, or that attempts will be made to remove the catheter from the body while the tip is in the protruded state, with consequent discomfort to the patient and damage to the body tissue.